DCHP/DNS server

bbarrick

When setting up a DHCP server, specifically I guess if it matters any on a Cisco router, what is the purpose of configuring a DNS server ip?

silverp1

The DHCP server will do a few things beyond assign IP's, it can also give hosts default gateways, DNS server IP's, domain names and a bunch of other stuff. By giving the DHCP server a DNS server address, it will provide this information to any host that requests it.

bbarrick

Ok, that makes sense. I had just read that but after reading through the configuration I lost track of the other things that it does. I was thinking maybe DHCP used the DNS server for something else. But it just uses the IP to the DNS, there's no real interaction between DNS and DHCP right?

iamme4eva

Correct. It tells the client where it's DNS server is.

Essentially, if you statically assign an IP in Windows, you get 5 boxes - the bottom two are the DNS server IP's. What you set on the DHCP server tells the client what to put in those boxes.

pamccabe

From what I understand, you can configure a cisco router to act as a dns server. However, it might be a CCNP related topic, because I've never read anything about it in any CCNA material.

bbarrick

pamccabe wrote: »

From what I understand, you can configure a cisco router to act as a dns server. However, it might be a CCNP related topic, because I've never read anything about it in any CCNA material.

It's on the CCENT now.

Mrock4

Example of configuring a router to function as a DNS server:

http://www.sgtccie.com/images/DNS_server.png (contains a screenshot of the config, as well as an example)

Topology is: R2

---

R3

---

R10

R3 is the DNS server, and the example shows R2 resolving R10 via R3.

theodoxa

I don't know if there's more that I don't know about, but my understanding is that DNS on a Cisco Router is very limited (no PTR, CNAME, DNAME, etc..., just A, MX, and SRV records) in what types of records you can create and I didn't see any way to create zones. I assume you just give the FQDN for each record. I'd just stick with BIND9 on a Linux box or VM.

Mrock4

I have never implemented DNS in a production environment on a router, and frankly don't see a reason to- just wanted to show it in action.

bbarrick

bbarrick wrote: »

It's on the CCENT now.

Oops, I should clarify DHCP configuration on a router is on the CCENT, not DNS.